1. Field of the Invention
The present invention relates to a method for measuring a distance to an object.
2. Description of the Related Art
A distance measurement apparatus has been known as disclosed in Japanese Laid-Open Publication No. S63-266382 that measures a distance to an arbitrary target (measurement object) based on a difference between a time at which laser light is irradiated to the target and a time at which the reflected light is received. By combining this distance measurement apparatus with a compass, a direction measurement apparatus can be structured that measures a direction of the target seen from a measurement point. A position measurement apparatus is also known as disclosed in Japanese Laid-Open Publication No. 2005-77291 that measures, based on electric waves from a plurality of GPS satellites on a geosynchronous orbit, a position on earth (latitude, longitude, and altitude).
The above known techniques have the following problems. Specifically, the distance measurement apparatus uses laser light that is hazardous to a human body (because laser light may damage optic nerves) and thus has a problem in safety. The position measurement apparatus using GPS satellites cannot be used in a place to which an electric wave cannot reach (e.g., indoor).